BackgroundHigh tidal volume can cause ventilator-induced lung injury (VILI), but positive end-expiratory pressure (PEEP) is thought to be protective. We aimed to find the volumetric VILI threshold and see whether PEEP is protective per se or indirectly.MethodsIn 76 pigs (22 ± 2 kg), we examined the lower and upper limits (30.9–59.7 mL/kg) of inspiratory capacity by computed tomography (CT) scan at 45 cmH2O pressure. The pigs underwent a 54-h mechanical ventilation with a global strain ((tidal volume (dynamic) + PEEP volume (static))/functional residual capacity) from 0.45 to 5.56. The dynamic strain ranged from 18 to 100 % of global strain. Twenty-nine pigs were ventilated with end-inspiratory volumes below the lower limit of inspiratory capacity (group “Below”), 38 within (group “Within”), and 9 above (group “Above”). VILI was defined as death and/or increased lung weight.Results“Below” pigs did not develop VILI; “Within” pigs developed lung edema, and 52 % died before the end of the experiment. The amount of edema was significantly related to dynamic strain (edema 188–153 × dynamic strain, R2 = 0.48, p < 0.0001). In the “Above” group, 66 % of the pigs rapidly died but lung weight did not increase significantly. In pigs ventilated with similar tidal volume adding PEEP significantly increased mortality.ConclusionsThe threshold for VILI is the lower limit of inspiratory capacity. Below this threshold, VILI does not occur. Within these limits, severe/lethal VILI occurs depending on the dynamic component. Above inspiratory capacity stress at rupture may occur. In healthy lungs, PEEP is protective only if associated with a reduced tidal volume; otherwise, it has no effect or is harmful.

BackgroundLung weight characterises severity of pulmonary oedema and predicts response to mechanical ventilation. The aim of this study was to evaluate the accuracy of quantitative analysis of thorax computed tomography (CT) for measuring lung weight in pigs with or without pulmonary oedema.MethodsThirty-six pigs were mechanically ventilated with different tidal volumes and positive end-expiratory pressures that did or did not induce pulmonary oedema. After 54 h, they underwent thorax CT (CTin vivo) and were then sacrificed and exsanguinated. Fourteen pigs underwent a second thorax CT (CTpost-exsang.) after exsanguination. Lungs were excised and weighed with a balance (balancepost-exsang.). Agreement between lung weights measured with the balance (considered as reference) and those estimated by quantitative analysis of CT was assessed with Bland-Altman plots.ResultsOne animal unexpectedly died before CTin vivo. In 35 pigs, lung weight measured with balancepost-exsang. was 371 ± 184 g and that estimated with CTin vivo was 481 ± 189 g (p < 0.001). Bias between methods was −111 g (−35%) and limits of agreement were −176 (−63%) and −46 g (−8%). Measurement error was similar in animals with (−112 ± 45 g; n = 11) or without (−110 ± 27 g; n = 24) pulmonary oedema (p = 0.88). In 14 pigs with thorax CT after exsanguination, lung weight measured with balancepost-exsang. was 342 ± 165 g and that estimated with CTpost-exsang. was 352 ± 160 g (p = 0.02). Bias between methods was −9 g (−4%) and limits of agreement were −36 (−11%) and 17 g (3%). Measurement errors were similar in pigs with (−1 ± 26 g; n = 11) or without (−12 ± 7 g; n = 3) pulmonary oedema (p = 0.12).ConclusionsCompared to the balance, CT obtained in vivo constantly overestimated the lung weight, as it included pulmonary blood (whereas the balance did not). By contrast, CT obtained after exsanguination provided accurate and reproducible results.

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Background and Study Aim: Advance biliopancreatic endoscopies are nowadays performed in non-operating room anesthesia (NORA) under general anesthesia (GA). We evaluate the outcomes of non-intubated patients in prone position who received GA for endoscopic ultrasound (EUS) and endoscopic retrograde cholangiopancreatography (ERCP) in a tertiary referral center for digestive endoscopy. Patients and Methods: Anesthesiological records, anamnestic, and intraoperative data of patients who underwent advanced therapeutic biliopancreatic endoscopies at our tertiary referral center from January 2019 until January 2020 were collected in the present observational study. Results: One hundred fifty-three patients (93 M; median age: 68-year-old; mean ASA status: 2) were considered eligible for a procedure in the prone position with GA in spontaneous breathing. Prone position was always the initial setting. Propofol administration through a target-controlled infusion (TCI) pump was the choice to achieve GA. In our experience, desaturation appears to be the most frequent adverse event, accounting for 35% of cases (55/153). Treatment foresaw additional oxygen through a nasopharyngeal catheter, which proved to be a sufficient measure in almost all patients (52/55). Other adverse events (i.e., inadequate sedative plan, pain, and bradycardia) accounted for 2.6% of cases (4/153). Conclusions: Non-intubated GA in the prone position may be regarded as a safe procedure, as long as the anesthesiological criteria of exclusion are respected and the anesthesiological team has become acquainted with the peculiar NORA setting and familiar with the management of possible adverse events.